Systems Engineering

A common method to document a system is to index all the requirements, plans, drawings, analyses, reports, budgets, work logs, and other data by a numbering system called a Work Breakdown Structure, which covers all the elements of the system across it's life cycle. In modern projects the actual data is mostly stored electronically, but a WBS helps organize and find particular items in the same way classification systems for books are used to organize libraries.

A WBS is a hierarchical table or drawing showing all the parts of a complex system and their successive division into smaller parts until you reach the level that specialty engineers can do the detailed design. It gives structure to what would otherwise be an amorphous mass of design work. The WBS serves as a tracking method and index, so that people working on different parts of the project tell they are talking about the same items. It also serves as a method to collect and file the engineering data as it accumulates, assign tasks to individuals and groups, and track progress and costs. The WBS is often derived from the functional analysis of the system.

In theory a WBS can be structured in any way you choose, but usually each level of division within the structure has a common basis. Examples include:

• By location on Earth or in Space
• By type of function, such as Production, Operation, and Transportation
• By type of element, such as Data, Software, Hardware, Facilities, and Staff.
• By end item product, such as a launch vehicle or lunar base
• By Subsystem, such as structures, mechanical, or electrical
• By time sequence, such as Phase I, or Version 2 Upgrade
• By type of data such as drawings, analyses, or reports

The basis to use depends on what makes sense for the project, but a consistent structure, such as all second level divisions are by end item, makes the overall structure easier to understand and use. It is more important that everyone on the project use the same structure than exactly how it is divided up. Maintaining the structure is often assigned to systems engineering specialists because it is related to the other tasks they perform. Each part of the structure is given a number or identifying key, typically using decimal points to distinguish levels, i.e 1,2,3, ... for the top level, then 1.1, 1.2, 1.3, ... for the parts that make up the next level below item 1, and so on. This is not the only way to do such structuring, but it is commonly used and easy to understand. The following section illustrates some of the ways to arrange a given WBS level. It is not an exhaustive list.

WBS by Item Type

This example is for an automated factory that consists of operating data, software, and hardware, facilities, and staff:

1.0 Operating Data Components

• 1.1 Design Standards
• 1.2 Manuals and procedures

2.0 Software Components

• 2.1 Design Software - A great deal of design software already exists. The specific need for advanced manufacturing is to design parts so they can fit the production capability of given machines, and supply processing and assembly instructions for individual and collections of parts. This may required modifying or adding to existing software.
• 2.2 Work Order Software - Takes an incoming product design in the form of CAD files, compares it to the factory capabilities and inventory, and generates a work order list of tasks for each machine, parts and materials to order, etc. Work orders are then scheduled among the various components.
• 2.3 Machine Driver Software - Each type of automated machine requires specific driver software to control how it operates, and to collect data back to track progress and other purposes.

3.0 Hardware Components

• 3.1 Storage - Materials, parts, and assemblies need to be stored when not actively being worked on.
• 3.2 Materials Handling - To transport items from one location to another.
• 3.3 Production Machines - Turn raw materials into inventory stock or finished parts, possibly using several machines for different steps.
• 3.4 Assembly Machines - Convert a collection of parts into a finished item. This will generally involve one or more robots.
• 3.5 Inspection and Observation Hardware - To test items and oversee operations.

4.0 Facility Components - This includes modification of the surroundings, controlling the factory environment using buildings, and supplying utilities, but not specifically producing any items.

5.0 Staff Components - Humans are not components to be designed, but rather selected and trained for required skills, and then supplied in needed numbers.

WBS by Subsystem Type

This example is a typical set of subsystems for space hardware, and also lines up with design specialties: